Bearing construction for roller hearth furnaces



Oct. 10, 1939. VAUGHAN} 2,175,233

BEARING CONSTRUCTION FOR ROLLER HEARTH FURNACES Filed Sept. 16, 1938 4 Sheets-Sheet 1 h i g l5 I? Oct. 10,1939. I V H I 2,175,233

BEARING CONSTRUCTION FOR ROLLER HEART FURNACES I Filed Sept. 16, 1938 4 Sheets-Sheet 2 2g N N m I *1 1 is l H N 5. ,6 i l I F: E @i Q! i- 1 Q l $1 a @1 I i 1 z 5 :6 I l OI P 1 *fi l -\I 8i m R g l Oct. 10, 1939; A. H. VAUGHAN BEARING CONSTRUCTION F OR ROLLER HEARTH FURNACES 4 Sheets-Sheet 3 'Filed Sept. 16, 1938 Oct. 10, 1939. A. H. VAUGHAN ,2

BEARING CONSTRUCTION FOR ROLI JER HEARTH FURNACES Filed Sept. 16, less 4 Sheets-Sheet 4' Patented Oct. 10, 1939 BEARING CONSTRUCTION FOR ROLLER HEABTH FURNACES Arthur H. Vaughan, Salem, Ohio, assignor to The Electric Furnace Company, Salem, Ohio, a corporation .of Ohio Application September 16, 1938, Serial No. 230,289

11 Claims.

The invention relates to furnaces and more particularly to special or controlled atmosphere furnaces and to an anti-friction bearing construction and mounting for driven conveyor rollers for such furnaces.

' It is customary to convey the articles or material being heated or heat treated in continuous furnaces through the heating and other zones of the continuous furnace installation by means of 19 a series of driven rollers usually termed conveyor rollers". Such an arrangement is usually-employed, for example, in furnace installations for annealing copper tubes, for copper brazing, for short-cycle malleableizing, and for normalizing 15 strip and sheet steel.

A furnace suitable for carrying out one of these operationsmay include a case or shell of steel plate and a lining of refractory material which defines an elongated, usually horizontal chamber 29 through which the material being treated is conveyed. A cooling chamber formed by water cooled or jacketed walls may extend from the heating chamber. A plurality of metal conveyor rollers, preferably constructed of a heat-resisting alloy, are disposed transversely of the heating and cooling chambers and extend through apertures in the refractory lining and/or shell of the heating chamber and through apertures in the cooling chamber walls.

30 Each conveyor roller is usually provided with a bearing at or near each end thereof, which bearings. are sometimes bolted directly to the shell plates or at other times are attached to a separate structure spaced from the shell plates. Various types of sealing means are frequently used to reduce leakage of gas and air through the apertures in the chamber walls and around the conveyor rollers.

Obviously, it is necessary to provide for the internal expansion and contraction of the conveyor rollers and of the furnace and to provide for such bearing misalignment as may-result ,from such expansion and contraction.

Bearing misalignment may also occur due to crookedness or camber of the conveyor rollers which almost invariably develops to some or a considerable extent in the operation of high temperature furnaces.

Even though the' conveyor rollers are constructed of a special heat resisting alloy, cost usually dictatesa conveyor roller design in which creep" or slow plastic deformation will take place if the rollers are permitted to remain stationary at high temperature for any extended 5 period of time.

Conveyor rollers which have become cambered in this way. will in most cases gradually return to substantial'straightness after' a period of operation, but it is absolutely essential that the Q bearing construction for such conveyor'rollers as brick dust from and retains lubricant within be such as to permitproper rotation of the rollers, even though the rollers are badly cambered.

Furthermore, the heat conducted through the metal walls of the conveyor rollers from the interiorof the furnace, to the exterior thereof, re- 5 quires the use of a conveyor roller bearing construction which will not excessively wear, seize, etc., under furnace operating conditions With the increased use of special atmosphere furnaces" these problems are multiplied by the requirement in a special atmosphere furnace of providing a gas-tight seal where the conveyor rollers extend through the chamber walls in order to prevent the loss or escape at this place of the relatively expensive special atmosphere main tained in the furnace.

Finally, in order to take advantage of the low rate of wear and the easy and uniform rotation of ball or other anti-friction bearings, it is-distinctly desirable to utilize such bearings for such conveyor rollers.

It is therefore a primary object of the present invention to overcome the diflicultiesand problems enumerated above, particularly in connection with the construction and operation of roller hearth furnaces and particularly special atmosphere roller hearth furnaces.

A further object of the present invention is to provide an improved self-aligning, anti-friction bearing construction and seal for roller hearth furnace conveyor rollers.

Various attempts have been made to provide sealing means for preventing leakage of special atmosphere from a furnace around a conveyor roller or through an anti-friction bearing therefor, where self-aligning bearings are used. However, the past attempts to solve this problem have. sacrificed sealing capacity for maximum selfaligning capacity or have sacrificed self-aligning capacity for maximum sealing capacity.

It is therefore a further object of the present invention to provide sealing means for preventing leakage of special atmosphere gas outward, or of air inward through or around a self-aligning bearing mounting for the conveyor rollers of a 45 special atmosphere roller hearth furnace which have a maximum sealing capacity and at the same time permits all or a large part of the selfaligning capacity of the bearings for the conveyor rollers to be utilized.

A further object of'the present invention is to provide sealing means 1 for conveyor rollers mounted in self-aligning, anti-friction bearings which eflectively excludes abrasive material such the bearing and prevents the'lubricant from creeping along the conveyor rollers into the furnace wall aperture traversed by the conveyor rollers.

Still another object of the present invention standard constructions of continuous furnaces of various types in a simplified and inexpensive manner and which satisfies one -or all of the objects set forth hereinabove.

The foregoing and other objects may be ob tained by the furnace, conveyor roller, bearing, and seal constructions, apparatus, parts, improvements, combinations and sub-combinations which comprise the present invention, the nature of which is set forth. in the following general statement, preferred embodiments of which, together with their mode of construction and operation, are set forth in the fOHOWulE' description, and which are particularly and distinctly pointed out and set forth in the appended claims forming part hereof.

The nature of the improvements of the present invention may be described in general terms as including in heating furnace construction, walls forming a material treating chamber or chambers such as a heating chamber or a cooling chamber, there being preferably aligned openin s in opposite chamber walls, a series of conveyor rollers traversing said chamber or chambers each roll having an end which extends through one of said openings and the other. end extending through an opposite aligned opening, a bearing housing secured in gas-tight relation to one of said walls about each opening at each end of each roller, an anti-friction hearing within each housing, each bearing including inner and outer races with rotatablebearing members rolling on and between said races, at least the inner race of each bearing being mounted on said roller free to oscillate about a point on the axis of rotation of the bearing and the roller, a sealing member within each housing journaled on the roller inter- -mediate the chamber and bearing, said sealing member and said housing having respectively convex and concave spherical surfaces whose common center of curvature is located at the center of oscillation of the inner race, preferably means holding said sealing member against rotation with respectto the housing about the axis of the roller, means for maintaining intimate contact between said spherical surfaces, preferably means for supplying lubricant to the bearing, preferably means for cooling the bearing and bearing housing, one end of each roller preferably extending through its bearing housing, means for driving said last mentioned end of each roller, and grease retaining sealing means between said roller and housing and between said bearing and drive means at said last mentioned end of each roller.

By way of example, several embodiments of the present improvements are illustrated in the accompanying drawings, forming part hereof, in which Figure 1 is a fragmentary side elevation of a special atmosphere roller hearth furnace and a portion of a cooling chamber extending from the furnace, equipped with the improved conveyor roller bearing construction, parts of the furnace and cooling chamber being broken away;

Fig. 2 is a' transverse section through the cooling chamber illustrated in Fig. 1, taken on the line 22, Fig. 1, showing a conveyor roller equipped with the improved bearing construction;

Fig; 3 is an enlarged view with parts in section through the bearing and a portion of the furnace wall, taken as on the line 3-3, Fig. 1, illustrating a preferred form of bearing at one end of a conveyor roller; I

Fig. 4' is a view similar to Fig, 3 illustrating a similar bearing construction for the other or drive end of the conveyor roller;

Figs. 5, 6 and 7 are views similar to Fig. 4 showing modified forms of the improved sealed selfaligning bearing construction; and

Fig. 8 is a fragmentary'elevation of a bearing seal spring used in the construction shown in Figs. 3 and 4.

Similar numerals refer to similar parts throughprovided with the usual doors and controls; and

the heating and cooling chambers may likewise be supplied with any desired special atmosphere.

The furnace l0 including the cooling duct I2 is provided with a roller hearth which includes a series of rollers l5. One end of each roller l5 has preferably mounted thereon a sprocket 16 (Fig. 1) which may be driven in the usual manner by a chain drive l1 including a hold down rail l8 and a return track l9.

In order that the rollers may be driven from the exterior of thefurnace, and properly journaled in anti-friction bearings, preferably each end of each roller l5 extends through an opening 20 formed in the refractory and shell walls Ha and Nb of the furnace; and similar openings 20a are provided in the walls I3 forming the cooling chamber. The openings 20 or 20a for each roller are preferably aligned openings in opposite chamber walls as the rollers l5 usually extend horizontally with the series of conveyor rollers l5 being located substantially in a horizontal plane.

Each conveyor roller l5 preferably includes a central cylindrical portion 2| terminating in tapered portions 22, which terminate in reduced end portions 23 and 23a. The end portion 23a on the drive end of each roller I5 is preferably again slightly reduced in diameter as at 23b and threaded at 230 for securing the sprocket wheel l6 thereon by nut 24.

A bearing housing 25 is bolted to the shell plate Ila or wall [3 on each side of the furnace or coolingduct, positioned about each opening 20 so as to surround or enclose the same; and each bearing housing 25 may preferably be formed of cast iron. Gaskets 26 may be interposed between housings 25 and shell walls Ila or l3 to insure a gas-tight joint between the housings 25 and the shell.

The housing 25 is bored at 25 to receive the internal self-aligning ball bearing 21 whose outer race is internallyground to provide a ball contact surface in the form of a spherical segment.

Such a self-aligning ball bearing 21 is of a well armass known form requiring no further description ex- 1 cept to state that the inner race thereof is free to oscillate about the geometrical center of the bearing indicated at 28, and thus compensate for both inaccurate mounting of the outer race and camber or misalignment of the roller l5. i

As shown in Fig. 3, the bearing housing at one end of each roller l5 may be enclosedby a usual cap 29. The bearing housings may be: and. preferably are formed with a cooling channel into which cooling medium may be introduced and circulated through pipe 3! and the interior of the housing may be lubricated and maintained with the proper amount of lubricant therein through lubricating fitting 32 and opening 33 leading therefrom.

At the drive end of each roller i5 (Fig. 4) ,the inner race of bearing 21 is held against shoulder 2311 by nut 24, which transmits pressure through sprocket i6 and a cylindrical spacer 34. A ring cap 29a through which the drive end 23b of roller l5 extends, secures the outer race of bearing 21 within bearing housing 25 at the drive end of each roller i5.

. grease grooves 31 for. preventing the escape of gas from the furnace between the sealing ring 35 and the roller, and these grooves also hinder the scape of lubricant from the bearing housing I Each sealing ring 35 is provided with a convex spherical surface 38, which fits against a cooperating concaved spherical surface 39 formed in the bearing housing 25, said spherical surfaces 38 and 39 having a common center of curvature coinciding .with the center of oscillation 28 of bearing 21.

Each sealing ring 35 is prevented from rotating about the axis of roller l5 by any suitable means such as by a pin 40 extending from housing 25 into an elongated slot Ii formed in ring 35. The slot H is, however, of such size and shape as to permit ring 35 to oscillate when the inner race of bearing 21 oscillates for selfalignment.

The spherical surfaces 38 and 39 are urged into intimate sealing contact at all times by spring fingers 42 formed in flat ring spring 43 (Fig. 8) which is clamped between the outer race of bearing 21 and housing 25; so that no lubricant can escape from housing 25 into the furnace chamber or no gas from the furnace chamber can escape through bearing housing between surfaces 33 and 39.

Referring to Fig. 4, the cap 29a may be counterbored to receive a ring 44 of felt, in, or other non-metallic packing material, which may be held. in place by retainer 45, for excluding dust from the bearing and retaining lubricant within the bearing housing at the drive end of each roller- Referring to Fig. 3, due to internal expansion and contraction which may take place longitudinally in each roller i5, the roller end 23 is machined to a diameter which will. slide freely through the inner race of bearing 21.

The construction shown in Fig. 5 is similar to that shown in Fig. 4, except that another usual type of self-aligning anti-friction concaved roller bearing 21a is utilized. The gas sealing ring construction 35 and the lubricant retaining seal M are the same in the construction shown in Fig. 5 as in the construction shown in Fig.4.

InFig. '1, a similar construction to that shown bearing oscillates, the outer surface of the outer 1 race being spherically formed on center 28. A modified form of sealing ring 351: is utilized, which abuts directly against the outer raceof bearing21b and a coil spring 93a reacts between cap member 29b to. urge the convex spherical surface of sealing ring 35a into sealing relation against the spherical surface formed in bearinghousing 25a. In Fig. 6, a modified form of outer lubricant retaining seal illustrated as comprising a usual piston ring s aling construction a. Having now described the features of the invention, the construction, operation and use of preferred forms of the same andthe'advantages and results obtained by the use of the same; the

new and useful parts, elements, combinations, 3

. constructions and devices, and reasonable mechanical equivalents thereof obvious to those skilled inthe art are set forth in the appended claims.

I claim: a

1. In a roller hearth heat treating furnace, walls forming a material treating chamber, there being openings in opposite walls, a conveyor roller tends through one of said openings, a bearing, housing secured to one of said walls about said openings at each end of said roller, and an antifriction bearing within each housing, each bearing including inner and outer races, said inner race being mounted on said roller and at least a traversing said chamber each end of which ex- 2. In a furnace, a conveyor roller, a bearing housing associated with an end of said roller;

an anti-friction bearing mounted within said housing including inner and outer races, the inner race being mounted on said roller and being free to oscillate about a point on the axis of rotation of the bearing, a sealing member within the housing and journaled on the roller adjacent to said anti-frictionbearing, said sealing member and said housing having respectively convex and concave spherical surfaces whose common center of curvature is located at the center of oscillation of the inner race, and means urging said sealing member spherical ,surface into intimate contact, with 'saidvhousing spherical surface.

3. In a roller hearth heat treating furnace, walls forming a material treating chamber, there being an opening intone ofsaid walls, a con veyor roller traversing said chamber hiving an end extending through said opening, a bearing housing for said roller end mounted on said wall around and enclosing said opening, an oscillatable self aligning, anti-friction bearing mounted ing member journaled on the roller within the- 4 within the housing and on said roller end, a seal-' sealing member journaled on the roller within the housing adjacent .to one side of said antifriction bearing, said sealing member being provided respectively with convex and concave spherical surfaces formed on a center coinciding with the center of oscillation of said bearing, means holding said sealing member against rotation about the axis of said bearing, means reacting between the housing and sealing member urging said spherical surfaces into gas-tight sealing contact, the end of said roller extending through said housing on the side of the bearing opposite to that side adjacent to which the sealing member is located, means for driving the extended end of said roller, and yielding lubricant sealing means interposed between the housing and roller and between the bearing and drive means.

5. In a furnace, a conveyor roller, 9. bearing housing associated with an end of said roller, an oscillatable self-aligning anti-friction bearing mounted within the housing and on said roller, a sealing member journaled on the roller within the housing adjacent to one side of said antifriction bearing, said sealing member being provided respectively with convex and concave spherical surfaces formed on a center coinciding with the center of oscillation of said bearing, means holding said sealing member against rotation about the axis of said bearing, means reacting between the housing and sealing member urging said spherical surfaces into gas-tight sealing contact, the end of said roller extending through said housing on the side of the bearing opposite to that side adjacent to'which the sealing member is located, means for driving-the extended end of said roller, and lubricant sealing means interposed between the housing and roller and between the bearing and drive means, the said lubricant sealing means including a member jonrnaled on the roller within the housing, said member and housing being provided respectively with convex and concave spherical surfaces formed on a center coinciding with the center of oscillation of said bearing, means holding said member against rotation about the axis of said-bearing, and means reacting between the housing and said member urging the spherical surfaces thereof into intimate contact.

6. In a furnace having a wall provided with an opening, a conveyor roller extending through said wall, means mounting an end of the roller including an oscillatable self-aligning, antifriction bearing, a member fixed with respect to said wall having a concave spherical surface, a sealing member journaled on said roller having a convex spherical surface, said spherical surfaces having a common center of curvature located at the center of oscillation of said bearing, and means for maintainingintimate contact between said spherical surfaces.

"I. In a furnace having a wall provided with an opening, a conveyor roller extending through said wall, means mounting an end of the roller including .an oscillatable self-aligning, antifriction bearing, a member enclosing said open.- ing having a concave spherical surface, a sealing member journaled on said roller having a convex spherical surface, said spherical surfaces having a common center of curvature located at the center of oscillation of said bearing, means for maintaining intimate contact between said spherical surfaces, and said roller being longitudinally axially movable with respect to said bearing member and sealing member to permit thermal expansion and contraction of said roller.

8. In a furnace having a wall provided with an opening, a conveyor roller extending through said wall, means mounting an end of the roller including an oscillatable self-aligning, antifriction bearing, a member fixed with respect to said wall having a concave spherical surface, a sealing member journaled on said roller having a convex spherical surface, said spherical surfaces having a commoncenter of curvature located at the center of oscillation of said bearing, means for maintaining intimate contact between said spherical surfaces and means for cooling said bearing.

9. In a furnace having a wall provided with an opening, a conveyor roller extending through said wall, means mounting an end of the roller including an oscillatable self-aligning, antifriction bearing having inner and outer raceways, said outer race being fixed and said inner spherical surface, a sealing member journaled on said roller having a convex spherical surface,

said spherical surfaces having a common center of curvature located at the center of oscillation of said bearing, and means for maintaining intimate contact between said spherical surfaces.

10. In a furnace having a wall provided with an opening, a conveyor roller extending through said wall, means mounting an end of the roller including a self-aligning, anti-friction bearing having inner and outer raceways both oscillatable about a point on the axis of rotation of the bearing, a member fixed with respect to said wall having a concave spherical surface, a sealing member joumaled on said roller having a convex spherical surface, said spherical surfaces having a common center of curvature located at the center of oscillation of said bearing, and means for maintaining intimate contact between said spherical surfaces.

11. In a furnace having a wall provided with an opening, a conveyor roller extending through said wall, means mounting an end of the roller including a self-aligning, anti-friction bearing having inner and outer raceways both oscillatable about a point on the axis of rotation of the bearing, a member fixed with respect to said wall having a concave spherical surface, a sealing the center of oscillation of said bearing, the outer I bearing raceway abutting said sealing member, and means reacting against said outer bearing raceway for maintaining intimate contact between said spherical surfaces.

ARTHUR H. VAUGHAN. 

